Refining of ferrochrome



Patent Jan. 22, 1924.

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- EEIEINING OF FEEBOCHROHE.

Ho Drawing.

"iRIcK, a subject of the King of Great Britain, residing at The Acacias,Higher Drive, Purley, Surrey, England, have in-.

vented new and useful Improvements in and Relating to the Refining ofFerrochrome, of

which the following is a specification. I The invention relates to therefining of ferro-chrome, whereby the carbon content ofi the alloy maybe reduced or eliminated.

According to the present inventionthe molten alloy is subjected to arefining blast or blowing operation by means of a gaseous mediumcontaining both oxidizing and reducing ga'ses'in the form of steam andhydrogen.

In addition to the use of hydro n and; steam, this gaseous admixture maye used in conjunction with other oxidizin gases, as for example, carbondioxide an air as oxidizing gases, and carbon monoxide as an additionalreducing gas.

This gaseous admlxture may be directed on to the surface of the moltenalloy, or injected or blown through the molten metal, or the gases maybe used for the refining operation in both of these ways.

In carrying out the refining operation according to the presentinvention, the molten alloy is preferably maintained within atemperature range of 1500 C. to 1600 C., and as near a temperature of1500 0., as possible. As the refining operation proceeds, a highertemperature may be necessary. But the temperature should not bepermitted to rise undulyhigh, as a lower temperature is more favourableto the productionof a refined alloy with a minimum loss of the chromiumcontent. The upper limit of temperature of the molten alloy should notexceed 1650 C., or 1700 (3., at the most.

All or part of the steam and hydrogen mixture may bedirected so as toimpinge on the surface of the molten alloy, in which case extremefluidity of the alloy may not be so necessary. I find a convenient wayof employing the I refining gases so as to work Within the desiredtemperature limits is to impinge a steam and hydrogen mixture on to thesurface of the molten alloy and to employ a more vigorous oxidizinggaseous refining admixture for blowing throughv the molten alloy. Thisblast through the alloy may be or cause Application filed January 17,1923. semi m. 613,292.

- A convenient form of refining blast withv in the scope of theinvention is producer gas, or f water gas, which a roportion of steamhas been added to be included therewith. Y As will be understood, thegaseous mixture employed according to my invention may .be preheated, inorder to avoid too strong a local cooling action at the pointcarbondioxide either In this way, the rise medium which imor blast furnacegases, to

where it is projected either through or on to the surface of the moltenalloy.

By the use of a blast containi both oxidizlng and reducing gases, as inti described, the carbon is subjected to an oxidizing action in thewell-known manner, while the reducing gas or gases exert a restrainingaction on the. oxidation of the metals of the molten alloy.

I am aware that inthe treatment of molten metals such as iron' or steelit known to use a blast of air or steam or both and to dissociate thesteam into its constituents but the treatment of ferro-chrome involvesconsiderations peculiar to this allo It is well known that this alloy isa-difiicu t e manner alloy to refine economically by reason of itsstrong afiinity for carbon, its high melting pomt, and its high chromiumcontent.

Vhen the high-carbon molten fined by treatment with an air hitherto beenproposed, the oxidatiou'of the carbon and silicon present as impuritiesrapalloy is reblast, as has idly raises the temperature of the moltenalloy to a point where severe oxidation of the chromium occurssimultaneously with an elimination of the oxidizable impurities. Thereis also a loss of chromium by evaporation at the high temperature of themolten bath. According to the process for the preparation of refinedferro-chrome constitutin the present invention, both hydrogen and steamare employed as a refining gaseous mixture and these ases ma be umeither with or without other suita le gas or ases as has hereinbeforebeen described. ile the steam is both an oxidizing agent and atemperature regulator, and particularly 9 as chrome to produce an alloywhen used in the manner described, the presenoe of hydro en in therefining blast pro- Vides for a iminished oxidation of the molten alloyconstituents thus permiting the blowing operation to be continued forsuch a period as will enable the molten alloy to be refinedsufi'iciently without severe losses of the chromium content, which is animportant consideration.

What it claim is 1. A process for refining molten ferrochrome to producean alloy of low carbon content, comprising, subjecting moltenferro-ohrome to the action of a gaseous mixture containing both hydrogenand steam.

2. A process according to claim 1, the molten ferro-chrome beingmaintained at a temperature of from 1500 C. to 1650 C.

3. A process for refining molten ferroof low carbon content, comprising,directing a blast 0th} drogen' and steam to impinge on the surface of abath of molten term-chrome.

4. A process for refining molten ferrochrome to produce an alloy of lowcarbon content, comprising, directing blasts of hydrogen and steambot-l1 upon the surface of a bath of molten 'ferro-chrome, and alsothrough the molten mass.

5. process for refining molten ferrochrome to produce an alloy of lowcarbon content, comprising, directingia blast of an oxidizing andreducing gas admixture onto the surface of a bath of molten term-chrome,and simultaneously directing a more highly oxidizing gas admixture ofoxidizing and reducing gases through the molten ferrochrome.

W. R. SALTRICK.

